Hi Lindy,
- Helix should get a new update that will include extra Web Accessibility fix, I hope in next 2-3 weeks.
- About SPPB yes, but ... as you know, all depends on website Editor.
If images don't have ALT or ALT is too short "image01" this is also mistake. The same if we talk about color-contrast, or text added on image (banner). Many small things can be wrong.
My free suggestion is... use Online Accessbility Testers (at least two) to check homepage and few main subpages, and correct what you can alone. Real Web Accessibilty Audits are EXPENSIVE.
Last thought ... none of the Accessibility Widgets will solve accessibility problems (!), it doesn't work this way, this is not "blue pill from Matrix" if you know what I mean.